Central neuraxial blocks (CNBs) remain the preferred anesthetic technique for cesarean section, with single shot spinal anesthesia (SSSA) being the standard practice at investigator's institute unless contraindicated. SSSA offers reliable intraoperative anesthesia and provides a few hours of postoperative analgesia. Enhanced recovery after cesarean section protocol has recommended the addition of intrathecal (IT) morphine to improve the postoperative quality of the recovery profile. Fentanyl improves the quality of intraoperative analgesia, while morphine significantly prolongs the postoperative pain relief, often lasting up to 24 hours.
Routine uterine exteriorization, practiced in all cases at investigator's institute, often results in peritoneal stretching pain during surgery. This visceral pain is managed with 10 mcg intrathecal fentanyl added to hyperbaric bupivacaine. For postoperative pain management, the intrathecal morphine is recommended by many guidelines and studies. Intrathecal morphine dose typically ranges from 50 to 300 mcg. The dose of morphine exceeding 150 mcg are usually associated with prolongation of analgesia with higher incidence of side effects like nausea, vomiting and pruritus. In selected cases, investigator had administered morphine 100-150 mcg and the clinical experience has shown reduced postoperative analgesic requirements and favorable recovery profile, with minimal adverse effects.
Despite these promising experiences and extensive literature on IT morphine, their is still lack formal data on the efficacy and safety profile of IT morphine in cesarean section patient. This comparative study will help institute to find the optimum dose of IT morphine with better postoperative analgesia quality with low side effects profile. The finding could serve as a foundation to promote routine use of intrathecal morphine in cesarean section anesthesia at investigator's institute.